The present invention relates to submunitions in general and, in particular, to a method and system for guiding submunitions.
Submunitions of various kinds, which are ejected or dispersed from a carrier, such as a missile, mortar or rocket, have long been known in the art. Generally, the carrier brings the submunitions to a location close to the target, and the submunitions are ejected or dispersed near the target. The submunitions either free fall from the ejection location relying on statistical distribution to hit the target, or include a guidance system to move them closer to the target. A number of methods are known for guiding the submunitions to the final target. One method employs terminal guidance systems, such as infrared seekers and other IR detection and guidance systems, as shown, for example, in U.S. Pat. No. 4,492,166.
Another method includes providing a mechanical control system, such as aerofoils or special wings with a target detector, such as those shown in U.S. Pat. No. 5,155,294 and U.S. Pat. No. 4,635,553.
There is shown in U.S. Pat. No. 4,554,871 to Allied Corporation a missile carrying at least two asymmetric submunitions. The guidance system on each submunition causes the submunition to precess about its center axis, thus creating an appropriate search pattern, or controlling the flight path of the submunition after a suitable target has been acquired by the submunition""s guidance system.
Satellite aided global location systems, such as the Global Positioning System (GPS) and Glonas, are also well known in the art. These utilize several satellites to permit a body on the earth to calculate, such as by triangulation, its precise location on the globe. Global location systems today are used in guidance systems for a wide variety of objects. These include munitions, such as bombs and missiles.
There is shown, for instance, in U.S. Pat. No. 5,943,009 to Northrop Grumman Corporation, a tail fin assembly for a munition having a housing configured for attachment to the munition, at least one flight control surface having an actuator, and a guidance system having a GPS receiver for effecting control of the actuator mechanism, so as to facilitate guiding of the munition.
U.S. Pat. No. 5,260,709 describes a system and method that uses differential computation of position relative to a GPS coordinate system and the computation of an optimum weapon flight path to guide a weapon to a non-moving fixed or relocatable target. The system comprises an airborne platform that uses a navigation subsystem that utilizes the GPS satellite system to provide the coordinate system and a synthetic array radar (SAR) to locate desirable targets. Targeting is done prior to weapon launch, the weapon therefore requires only a navigation subsystem that also utilizes the GPS satellite system to provide the same coordinate system that the platform used.
There is shown in U.S. Pat. No. 5,507,452 a precision guided system suitable for use in conventional aircraft launched bombs. The system includes a kit mounted upon the nose of the conventional bomb which replaces the conventional fuse disposed in a fuse well, the kit including guidance electronics controlling a self-contained jet reaction device and GPS P-code receiver electronics. The bombs are readied for discharge by signals broadcast from the aircraft into the bomb bay which transfer initial GPS data and commence operation of a gas generator which powers the jet reaction device.
All these systems include use of satellite aided global location systems to guide a relatively large, heavy munition, for example, a typical artillery shell which weighs about 50 kilos, flying at a speed of 400-500 meters/second, generally over a relatively long distance. Thus, the electronics and control system required to guide the munition are complex and expensive to manufacture and maintain.
It is an object of the present invention to provide a relatively simple and inexpensive method of guiding a submunition to its target after ejection from its carrier. This is accomplished by utilizing a satellite aided global location system (i.e., GPS or Glonas) guidance system for each submunition itself, rather than for the carrier munition.
There is provided according to the present invention a submunition for delivery in a carrier, the submunition including a satellite aided global location system guidance system mounted on the submunition for guiding the submunition towards a pre-selected target after delivery to a target area by the carrier.
According to a preferred embodiment, the satellite aided global location system guidance system includes a servo system, a global location system receiver, and a processor coupled to the servo system and to the global location system receiver.
According to a preferred embodiment of the invention, the submunition further includes inertial sensors.
There is also provided a method for guiding a submunition after delivery from a carrier, the method including mounting a satellite aided global location system guidance system on the submunition and utilizing the satellite aided global location guidance system to guide the submunition towards a pre-selected target.
According to one embodiment of the invention, the satellite aided global location system guidance system includes a servo system; a global location system receiver; and a processor coupled to the servo system and to the global location system receiver; and the step of utilizing the satellite aided global location system guidance system includes programming a pre-selected target point and flight path to the target point into the processor of each submunition; after the submunition is released, receiving signals from satellite aided global location system satellites in the global location system receiver; calculating the actual location of the submunition from the received signals; comparing the actual location with the desired location on the programmed flight path; and, if the actual location differs from the desired location, altering the actual flight path so as to guide the submunition to the pre-selected target point.